I have a 6.8 gig blu-ray .mkv video of Knowing and I'm wanting to encode this to at least a 4.5 gig .avi file to burn to a dvd. Anyone know the best and fastest way to do this? Thanks all who answer.

Super will do it for you.

For the life of me I can't figure out how to get it down to 4.5 gigs!!! Screw it I'm just going to download your parts and join them

Found this on another forum:
"You have to re-encode either a video or audio stream to use less space. If you go down the video route, you can get more savings quickly. If you go down the audio route, you will have to re-encode more files to save the same space.

The 4.7 vs 4.38 is a well worn arguement. It comes down to HDD and media manufacturers using 1000 instead 1024 as their base measure. It makes the capacity seem larger than it truely is. Nothing you can do about it.

You do have other options, inclusing using two discs, or looking at DL layer discs."

Though I've only converted a few files, what it comes down to is the output file type, video codec, and audio codec.
Each one affects the quality of the conversion, and the file size. Smaller file size usually means lower quality.

You may find these two links from the DVDs section of the Qss Toolkit helpful:
Convert A Downloaded File To A DVD
Rip A DVD To A divx, avi or wmv File Onto The Hard Drive